Canola protein isolates can be formed from canola oil seed meal. In copending U.S. patent application Ser. Nos. 10/137,391 filed May 3, 2002 (US Patent Application Publication No. 20030125526A1), 10/476,230 filed Jun. 9, 2004 (US Patent Application Publication No. 20040254353A1) and corresponding PCT Publication No. WO 02/089597, both assigned to the assignee hereof and the disclosures of which are incorporated herein by reference, there is described a method of making canola protein isolates from canola oil seed meal, such isolates having at least 100 wt % protein content (N>6.25). The procedure involves a multiple step process comprising extracting canola oil seed meal using a salt solution, separating the resulting aqueous protein solution from residual oil seed meal, increasing the protein concentration of the aqueous solution to at least about 200 g/L while maintaining the ionic strength substantially constant by using a selective membrane technique, diluting the resulting concentrated protein solution into chilled water to cause the formation of protein micelles, settling the protein micelles to form an amorphous, sticky, gelatinous gluten-like protein micellar mass (PMM), and recovering the protein micellar mass from supernatant having a protein content of at least about 100 wt % as determined by Kjeldahl nitrogen (N×6.25). As used herein, protein content is determined on a dry weight basis. The recovered PMM may be dried.
In one embodiment of the process described above, the supernatant from the PMM settling step is processed to recover a protein isolate comprising dried protein from the wet PMM and supernatant. This procedure may be effected by initially concentrating the supernatant using ultrafiltration membranes, mixing the concentrated supernatant with the wet PMM and drying the mixture. The resulting canola protein isolate has a high purity of at least about 90 wt % of protein (N×6.25), preferably at least about 100 wt % protein (N×6.25).
In another embodiment of the process described above, the supernatant from the PMM settling step is processed to recover a protein from the supernatant. This procedure may be effected by initially concentrating the supernatant using ultrafiltration membranes and drying the concentrate. The resulting canola protein isolate has a high purity of at least about 90 wt % protein (N×6.25), preferably at least about 100 wt % protein (N×6.25).
The procedures described in the aforementioned US Patent Applications are essentially batch procedures. In copending U.S. patent application Ser. No. 10/298,678 filed Nov. 19, 2002 (US Patent Application Publication No. 20040039174A1) and corresponding published International Application No. WO 03/043439, assigned to the assignee hereof and the disclosures of which are incorporated herein by reference, there is described a continuous process for making canola protein isolates. In accordance therewith, canola oil seed meal is continuously mixed with a salt solution, the mixture is conveyed through a pipe while extracting protein from the canola oil seed meal to form an aqueous protein solution, the aqueous protein solution is continuously separated from residual canola oil seed meal, the aqueous protein solution is continuously conveyed through a selective membrane operation to increase the protein content of the aqueous protein solution to at least about 200 g/L while maintaining the ionic strength substantially constant, the resulting concentrated protein solution is continuously mixed with chilled water to cause the formation of protein micelles, and the protein micelles are continuously permitted to settle while the supernatant is continuously overflowed until the desired amount of PMM has accumulated in the settling vessel. The PMM is removed from the settling vessel and may be dried. The PMM has a protein content of at least about 90 wt % as determined by Kjeldahl nitrogen (N×6.25), preferably at least about 100 wt % (N×6.25).
As described in the aforementioned U.S. patent application Ser. Nos. 10/137,391 and 10/471,230, the overflowed supernatant may be processed to recover canola protein isolate therefrom.
Canola seed is known to contain about 10 to about 30 wt % proteins and several different protein components have been identified. These proteins are distinguished by different sedimentation coefficients (S). These known and identified proteins include a 12S globulin, known as cruciferin, and a 2S storage protein, known as napin.
Canola is also known as rapeseed or oil seed rape
In copending U.S. patent application Ser. Nos. 10/413,371 filed Aug. 25, 2003 (US Patent Application Publication No. 20040034204) and 10/510,766 filed Apr. 15, 2003 as well as the corresponding published PCT Publication No. WO 03/08876 assigned to the assignee hereof and the disclosure of which is incorporated herein by reference, there is described the composition of the PMM canola protein isolate and of the supernatant-derived canola protein isolate. The supernatant-derived canola protein isolate is comprised mostly of the 2S protein with smaller amounts of 7S protein and a trace amount of 12S protein. The 2S protein is a low molecular weight albumin. The PMM produced is comprised predominantly of the 7S protein with 2S protein and 12S protein being relatively minor components. The 7S and 12S protein are higher molecular weight globulins with the 7S molecule being the half molecule of the 12S protein.
As described therein, the supernatant-derived canola protein isolate exhibits a protein profile which is:
about 60 to about 95% wt % of 2S protein,
about 5 to about 40 wt % of 7S protein, and
0 to about 5 wt % of 12S protein, preferably
about 70 to about 95 wt % of 2S protein,
about 5 to about 30 wt % of 7S protein, and
0 to about 2 wt % of 12S protein.
The PMM canola protein isolate exhibits a protein profile which is:
about 60 to about 98 wt % of 7S protein,
about 1 to about 15 wt % of 12S protein, and
0 to about 25 wt % of 2S protein, preferably
about 88 to about 98 wt % of 7S protein,
about 1 to about 10 wt % of 12S protein, and
0 to about 6 wt % of 2S protein.
It has been found that the supernatant-derived canola protein isolate consisting predominantly of 2S protein exhibits superior functional properties for certain applications than the PMM-derived canola protein isolate consisting predominantly of 7S protein. In the procedures described in the prior applications, in order to produce the supernatant-derived canola protein isolate, it was necessary to go through the steps of PMM formation and provision of a supernatant in order, in effect, to fractionate the canola proteins.
In U.S. patent application Ser. No. 11/038,086 filed Jul. 21, 2005 (U.S. Patent Application Publication No. US 2005-0181112A1), assigned to the assignee hereof and the disclosure of which is incorporated herein by reference (WO 2005/067729), there is described a procedure in which the supernatant from the PMM precipitation is, following membrane processing, subjected to heat treatment to precipitate the 7S protein and leave a protein solution enriched in 2S protein. The remaining solution may be spray dried.
The 2S protein having a minimal proportion of the 7S and 12S proteins demonstrates increased solubility over the untreated 2S protein at acid pH values and is able to provide improved clarity in solution and with soft drinks, providing clear protein fortified beverages.